1. Field of the Invention
This invention relates to umbrellas, and more particularly, to an umbrella with auto-opening mechanism that allows the umbrella, after being folded, to be opened automatically without manual effort from the user The particular design of the foldable frame structure allows the umbrella to be longer in life of use than the prior art.
2. Description of Related Art
A foldable umbrella allows the user to fold the umbrella when the umbrella is not in use for easy storage or carriage. Foldable umbrellas are typically provided with a auto-opening mechanism that allows the umbrella, after being foldable, to be opened automatically without manual effort from the user. Conventional foldable umbrellas, however, can easily fail in the auto-opening mechanism due to a poor structure in the foldable frame structure, which will be illustratively described in the following with reference to FIG. 5.
FIG. 5 shows a conventional foldable frame structure for a auto-opening umbrella. As shown, the foldable frame structure for auto-opening umbrella includes a main shaft 100, a bottom running hub 101, a spiral spring 102, an intermediate running hub 103, an upper running hub 104, a radiating frame of main ribs 105 (only one is shown), a frame of supporting ribs 106 (only one is shown), and a frame of linkage beams 108 (only one is shown). The upper running hub 104 is fixed on the top of the main shaft 100. The bottom running hub 101 and the intermediate running hub 103 are slidably mounted on the main shaft 100, with the spiral spring 102 mounting between the bottom running hub 101 and the intermediate running hub 103 for providing a auto-opening force for the umbrella. The main ribs 105 each radiates from the upper running hub 104 to form a frame for supporting the shielding fabric (not shown) of the umbrella. The supporting ribs 106 each radiates from the intermediate running hub 103 to support one of the main ribs 105 through a pivot joint 107; and the linkage beams 108 are each connected between the bottom running hub 101 and the mid-point of one ofthe supporting ribs 106, such that when the bottom running hub 101 is pulled down, the linkage beams 108 can draw the supporting ribs 106 and thus the main ribs 105 downwards to fold the umbrella. Each linkage beam 108 is affixed to the associated supporting rib 106 by means of a pin 109 which is fastened in position through holes 1061 formed in the middle portion of the supporting ribs 106 and a hole 108A formed in the end of the linkage beam 108. The supporting ribs 106 are typically made from a light-weight metal into thin, substantially U-shape pieces for the purpose of making the umbrella light-weighted. The auto-opening mechanism of the umbrella is driven by the spiral spring 102, which will be compressed when the umbrella is folded.
One drawback to the foregoing foldable frame structure of FIG. 5, however, is that during the operation of the auto-opening mechanism, a big amount of force applied from the restoration of the compressed spiral spring 102 to uncompressed state can cause the pin 109 and the holes 1061 to be deformed and loosened from position gradually from time to time, thus using for a period of time, it will break apart the connection between the linkage beams 108 and the supporting ribs 106. This is because that the supporting ribs 106 are made from thin and light-weighted metal pieces, which makes the pivotal coupling between the supporting ribs 106 and the linkage beams 108 by means of the pin 109 and the holes 1061 to be quite vulnerable and insecure. When the pivotal coupling between the linkage beams 108 and the supporting ribs 106 are broken, the umbrella would no longer be usable.